The present invention relates to systems using electrodes in the deposition of a dielectric material on a substrate.
In such a system, the pressure is typically reduced from atmospheric pressure by a vacuum pumping system. Electrode surfaces are in electrical communication with gases introduced into the system such that an electrical discharge or plasma is formed. The purpose of this discharge is to excite moieties in the system and cause them to be deposited onto the workpiece or substrate to be coated.
One problem in such systems is that the electrodes can become contaminated with an insulating layer of the dielectric material intended for the substrate. The growth of dielectric deposits on the electrodes will result in a shift of the voltage/current characteristics of the system over time. The required operating voltage will increase for a given current as contamination of the electrode progresses. These changes cause a drift in the quality of the dielectric coating produced on the substrate, and require periodic cleaning of the electrodes. Furthermore, due to the high impedance presented to the plasma by a contaminated electrode, power will be wasted and excess heat generated. It is desired to have a process free of drift with a minimum of waste heat generated.